Etchant composition

ABSTRACT

An etchant composition for wet etching a titanium-containing film. The etchant composition includes hydrofluoric acid as a primary oxidant, a co-oxidant that forms a dense oxide film on a surface of a titanium film during an etching process, an alkali metal salt that inhibits aggregation and adsorption of titanium ions during the etching process, and a solvent.

RELATED APPLICATIONS

This application is a National Phase of PCT Patent Application No.PCT/CN2019/083773 having International filing date of Apr. 23, 2019,which claims the benefit of priority of Chinese Patent Application No.201910098520.3 filed on Jan. 31, 2019. The contents of the aboveapplications are all incorporated by reference as if fully set forthherein in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

The present application relates to the field of display paneltechnology, and in particular to an etchant composition for use in adisplay panel process.

An organic electroluminescent diode display device is widely used in thedisplay field due to its self-luminous, simple structure, ultra-thin,fast response time, wide viewing angles, low power consumption, and therealization of a flexible display panel. As the demand for organic lightemitting diodes (OLEDs) continues to increase, production cost of OLEDsis required to be further reduced. Currently, the production cost ofOLEDs is influenced by equipment procurement and operating costs.

The requirement for the line width specification of an organic lightemitting diode (OLED) is relatively strict. In addition, etching processof the OLED requires simultaneously etching a plurality kind of metalfilms. Currently, there are few etchant compositions in the market canmeet the needs for simultaneously etching a plurality kind of metalfilms. Further, a metal titanium film and a titanium alloy film that aremain etching targets are highly resistant to etch. The etching ratethereof in a wet etching is difficult to control, such that theapplication of wet etching is limited. Thus, at present, dry etchingprocess is mainly used for simultaneous etching of a plurality kind ofmetal films. However, the cost of the dry etching process is high,resulting in the high production cost of OLED products. Therefore, thereis a need for a new etchant composition that satisfies the requirementfor the line width specification and the etching of multiple metal filmlayers, enabling replace dry etching with wet etching, such thatreducing the cost of equipment procurement and operating costs.

SUMMARY OF THE INVENTION

The purpose of the present application is to provide an etchantcomposition for etching a multilayer metal film, such as titaniumfilm/aluminum film/titanium film, by using a wet etching process insteadof a dry etching process in a touch panel process to reduce equipmentcost and production and cost, and improve production efficiency.

In order to achieve the object, according to an aspect of the presentapplication, an etchant composition for wet etching atitanium-containing film is provided. The etchant composition includeshydrofluoric acid as a primary oxidant, a co-oxidant that forms a denseoxide film on a surface of a titanium film during an etching process, analkali metal salt that inhibits aggregation and adsorption of titaniumions during the etching process, and a solvent.

In one embodiment, the etchant composition, based on total percentage byweight, includes hydrofluoric acid of 0.5-3%, the co-oxidant of 30-55%,the alkali metal salt of 1-5%, and remaining % of the solvent.

In a preferred embodiment, the etchant composition includes hydrofluoricacid of 2-3%, relative to the total weight of the etchant composition.For example, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, and 2.9%.

In a preferred embodiment, the etchant composition, based on totalpercentage by weight, includes an alkali metal salt of 1-3%, forexample, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%,2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, and 2.9%.

In one embodiment, the co-oxidant is a mixture of at least two acids.

In one embodiment, the co-oxidant is a mixture of halogen acid andoxyacid.

In one embodiment, the halogen acid is one of perbromic acid andperchloric acid or a combination thereof.

In one embodiment, the oxyacid is nitric acid.

In one embodiment, the etchant composition, based on total percentage byweight, includes nitric acid of 1-5% by weight, and perchloric acid of30-50% by weight.

In a preferred embodiment, the etchant composition, based on totalpercentage by weight, includes nitric acid of 2-3%. For example, 2.1%,2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, and 2.9%.

In a preferred embodiment, the etchant composition, based on totalpercentage by weight, includes perchloric acid of 35-45%. For example,36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, and 44%.

In one embodiment, the solvent is deionized water.

In one embodiment, the alkali metal salt is sodium nitrate.

In a preferred embodiment, an etchant composition is provided, relativeto the total weight of the etchant composition, the etchant compositionincludes hydrofluoric acid of 0.5-3%, nitric acid of 0.5-5%, perchloricacid of 30-50%, sodium nitrate of 1-5%, and deionized water of remaining%.

In a preferred embodiment, relative to the total weight of the etchantcomposition, the etchant composition includes hydrofluoric acid of 2-3%,sodium nitrate of 1-3%, nitric acid of 2-3%, perchloric acid of 35-45%,and deionized water of remaining %.

According to another aspect of the present application, providing anapplication of the etchant composition in the wet etching of atitanium-containing film. For example, an application for etching a filmcontaining titanium in a thin film transistor (TFT) array substrate. Thetitanium-containing film refers to a film including titanium in thecomposition and includes a single layer film or a multilayer film of adouble layer film or more. The titanium-containing film may be, but notlimited to, a single layer film of a titanium film or a titanium alloyfilm, or a multilayer film composed of a single layer film of a titaniumfilm or a titanium alloy film and an aluminum film.

A titanium alloy film is mainly composed of a titanium film. Thetitanium alloy film may include Nd, Cu, Pd, Ni, and Mg, etc. and anitride, an oxide, or a carbide thereof, but is not limited thereto.

In one embodiment of the present application, the titanium-containingfilm may be a multilayer film of an aluminum film/titanium film, atitanium film/aluminum film/titanium film, a titanium film/aluminumfilm, or an aluminum film/titanium film/aluminum film.

Beneficial Effect

In the present application, an etchant composition capable ofsimultaneously etching the titanium-containing multilayer film (such asmultilayer film of aluminum film/titanium film, titanium film/aluminumfilm/titanium film, titanium film/aluminum film, or aluminumfilm/titanium film/aluminum film) is obtained by the rational selectionof components and the synergy between the components.

The etchant composition described in the present application can be usedfor etching multilayer metal film of titanium film/aluminumfilm/titanium film. By using a wet etching process instead of a dryetching process in a touch panel process to reduce equipment cost andproduction cost and improve production efficiency.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in theembodiments of the present invention, the following figures described inthe embodiments will be briefly introduced. It is obvious that thedrawings described below are merely some embodiments of the presentinvention, other drawings can also be obtained by the person ordinaryskilled in the art based on these drawings without doing any creativeactivity.

FIG. 1 is a polarization curve measured by a titanium electrodepassivated at the various potential for various time, forming an oxidefilm in a 1.0 mol/L HClO₄ solution; and

FIG. 2 is a polarization curve of a titanium electrode at various scanrates in a mixed solution of 0.1 mol/L NaF and 0.1 mol/L NaClO₄.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The embodiments of the present invention are described in detail below,and the examples of the embodiments are illustrated in the drawings,wherein the same or similar reference numerals indicate the same orsimilar elements or elements having the same or similar functions. Theembodiments described below with reference to the drawings areexemplary, for the purpose of explaining the invention only and it isnot to be construed as limiting the invention.

In the present invention, unless expressly stated and limited otherwise,“the first feature is above/below the second feature” may indicates thatthe first feature directly contacts the second feature, and may alsoindicates that the first feature indirectly contacts the second feature,for example, the first feature contacts the second feature by anotherfeature between them. In addition, “the first feature above the secondfeature” may indicates that the first feature is directly above orobliquely above the second feature, or merely indicates that the levelof the first feature is higher than the level of the second feature, and“the first feature below the second feature” may indicates that thefirst feature is directly below or obliquely below the second feature,or merely indicates that the level of the first feature is lower thanthe level of the second feature.

The following disclosure provides various embodiments or examples forimplementing various structures of the present invention. In order tosimplify the disclosure of the present invention, the components andarrangements of the specific examples are described below. They aremerely examples and are not intended to limit the invention.Furthermore, the present invention may repeat reference numerals and/orreference letters in various examples. The repetition is for the purposeof simplification and clarity, and does not indicate the relationshipbetween the various embodiments and/or arrangements discussed. Moreover,the present invention provides examples of various specific processesand materials, but one of ordinary skill in the art will recognize theuse of other processes and/or the use of other materials.

In the present embodiment, an etchant composition for wet etching atitanium-containing film is provided. The etchant composition includes aprimary oxidizing agent, a co-oxidizing agent, an alkali metal salt, anda solvent.

The primary oxidizing agent is hydrofluoric acid (HF), and when etchinga single layer film or a multilayer film, it functions to oxidize thetitanium film and perform wet etching. The hydrofluoric acid is in anamount of 0.5-3%, preferably 1-2%, based on the total weight of theetchant composition.

Experiments show that only hydrofluoric acid is dissociated during anetching process, and its hydrogen ions participate in the etchingreaction so that a proportion of the hydrofluoric acid needs to becontrolled in the process. When the hydrofluoric acid is too small,nitric acid will participate in the etching of the aluminum metal film.If the content of the hydrofluoric acid is less than 0.5%, the etchingability of the etchant composition is insufficient, which may result ina decrease in etching rate and a poor etching profile. Further, if thecontent of hydrofluoric acid exceeds 4%, an etching rate of the aluminumfilm in the titanium-containing film is decreased, and an etching rateof the titanium film or the titanium alloy film becomes too fast,resulting in an etching angle to be polygonal, and the subsequentnon-metal film covering will collapse or has void.

The co-oxidizing agent is nitric acid and perchloric acid. The nitricacid is in an amount of 1-5%, preferably 2-3%, based on a total weightof the etchant composition. The perchloric acid is contained in anamount of 30-50%, preferably 35-45%.

The nitric acid (HNO₃) acts to oxidize a surface of the titanium filmand the aluminum film during the etching process to form a dense oxidefilm, thereby decreasing the etching rate. It has been experimentallyfound that if the content of the nitric acid exceeds 5%, the oxide filmformed by the titanium film/aluminum film is too dense, resulting in adecrease in the etching rate. The etching uniformity of the substrate isdeteriorated, such that a problem of streaking may occur. If the contentof the hydrofluoric acid is less than 1%, the undercutting problem ofaluminum film may be caused because the etching rate is too fast.

Please refer to FIG. 1. FIG. 1 shows the polarization curves (scan with50 mV/s) of a titanium electrode passivated at various potentials forvarious times in HClO₄ solution of 1.0 mol/L, and an oxide film isformed on the titanium electrode. FIG. 1 shows that the anodic oxygenevolution reaction causes the formation of oxides on a surface of thetitanium film. With the oxygen evolution reaction and the formation ofperoxide on the surface of the titanium film, a very thin insulatinglayer is formed on an outermost layer of the oxide surface to form apassivation layer. The oxide is stable and irreversible, which decreasesthe etching rate. Therefore, the perchloric acid (HClO₄) serves to forma dense oxide film on the surface of the titanium film during etching toretard an etching rate of the titanium film.

It has been experimentally found that in the case where the content ofthe perchloric acid is less than 30%, there is a problem of streaks dueto uneven etching speed in the substrate. On the other hand, in the casewhere the content of the perchloric acid is more than 50%, a largenumber of bubbles are generated during the etching, and an oxide film ona surface of the titanium film becomes too dense to cause the etchingrate decrease.

The alkali metal salt is sodium nitrate (NaNO₃). The sodium nitrate isin an amount of 1-5%, preferably 1-3%, based on a total weight of theetchant composition.

Please refer to FIG. 2. FIG. 2 is a superposition of polarization curvesof titanium electrodes at various scan rates in a mixed solution of 0.1mol/L NaF and 0.1 mol/L NaClO₄. As shown in FIG. 2, after adding sodiumfluoride to the base solution of sodium perchlorate of 0.1 mol/L, thepolarization current is significantly increased than that in the sodiumperchlorate solution of 0.1 mol/L, indicating that the addition offluoride ions does not change the passivation process of the titaniumelectrode surface. The fluoride ion reacts with the titanium film on asurface of the titanium electrode to form a complex TiF₆ ²⁻, whichaccelerates the dissolution of the titanium film when fluoride ions arepresent. Therefore, the sodium nitrate acts to accelerate the reactionrate of the titanium film during an etching process, while inhibitingthe aggregation and re-adsorption of titanium ions, and the etching rateis adjusted to achieve etching uniformity.

It has been experimentally found that in the case where a content ofsodium nitrate is less than 1%, there is a problem that the etchinguniformity in the substrate is decreased. In the case where a content ofsodium nitrate is more than 5%, a reaction rate of the titanium film andthe aluminum film is inconsistent due to an increase of the etchingrate.

The solvent is water, preferably deionized water.

Thus, in this embodiment, an etchant composition is provided, relativeto the total weight of the etchant composition, includes hydrofluoricacid of 0.5-3%, nitric acid of 0.5-5%, perchloric acid of 30-50%, sodiumnitrate of 1-5%, and deionized water of remaining %. More preferably,relative to a total weight of the etchant composition, the etchantcomposition includes hydrofluoric acid of 2-3%, sodium nitrate of 1-3%,nitric acid of 2-3%, perchloric acid of 35-45%, and deionized water ofremaining %.

The embodiment also provides an application of etchant composition inthe wet etching of a titanium-containing film. For example, anapplication for etching a film containing titanium in a thin filmtransistor (TFT) array substrate. The titanium-containing film refers toa film including titanium in the composition and includes a single layerfilm or a multilayer film of a double layer film or more. Thetitanium-containing film may be, but not limited to, a single layer filmof a titanium film or a titanium alloy film, or a multilayer filmcomposed of a single film of a titanium film or a titanium alloy filmand an aluminum film. A titanium alloy film is mainly composed of atitanium film, and the titanium alloy film may include Nd, Cu, Pd, Ni,and Mg etc., and a nitride, an oxide, or a carbide thereof, but is notlimited thereto. The titanium-containing film may be a multilayer filmof an aluminum film/titanium film, a titanium film/aluminumfilm/titanium film, a titanium film/aluminum film, or an aluminumfilm/titanium film/aluminum film.

Taking the touch panel production factory as an example, the equipmentinvestment cost of the dry etching equipment is about 150 million yuan(RMB) under a condition of 45K capacity. With the wet etching using theetchant composition described in the present application, the equipmentinvestment cost is only about 20 million yuan. In addition, theoperating cost of the wet etching equipment is also slightly less thanthat of the dry etching equipment.

In the present application, an etchant composition capable ofsimultaneously etching a plurality of layers of the titanium-containingfilm (such as multilayer films of aluminum film/titanium film, titaniumfilm/aluminum film/titanium film, titanium film/aluminum film, oraluminum film/titanium film/aluminum film) is obtained by rationalselection of components and synergy between the components. Therefore,the etchant composition described in the present application can be usedfor etching multilayer metal film of titanium film/aluminumfilm/titanium film. By using a wet etching process instead of a dryetching process in a touch panel process to reduce equipment cost andproduction cost and improve production efficiency.

The description of the above exemplary embodiments is only for thepurpose of understanding the invention. It is to be understood that thepresent invention is not limited to the disclosed exemplary embodiments.It is obvious to those skilled in the art that the above exemplaryembodiments may be modified without departing from the scope and spiritof the present invention.

INDUSTRIAL APPLICABILITY

The subject of the present application can be manufactured and used inthe industry and has industrial applicability.

What is claimed is:
 1. An etchant composition, based on total percentageby weight, comprising: hydrofluoric acid of 2-3% by weight, nitric acidof 2-3% by weight, perchloric acid of 35-45% by weight, sodium nitrateof 1-3% by weight, and a solvent of remaining % by weight, wherein thesolvent is deionized water.
 2. An etchant composition for etching atitanium-containing film, wherein the etchant composition compriseshydrofluoric acid as a primary oxidant, a co-oxidant that forms a denseoxide film on a surface of a titanium film during an etching process, analkali metal salt that inhibits aggregation and adsorption of titaniumions during the etching process, and a solvent; wherein the etchantcomposition, based on total percentage by weight, comprises hydrofluoricacid of 0.5-3% by weight, nitric acid of 1-5% by weight, perchloric acidof 30-50% by weight, the alkali metal salt of 1-5% by weight, andremaining % by weight of the solvent; wherein the alkali metal salt issodium nitrate, the co-oxidant is a mixture of nitric acid andperchloric acid, and the solvent is deionized water.
 3. A use of theetchant composition according to claim 2 to etch a titanium-containingfilm.
 4. The use according to claim 3, wherein the titanium-containingfilm is a single layer titanium film or a multilayer film comprising atleast one titanium film.